Mortarless masonry blocks have been known and used for many years. They are quite popular because they do not require extensive site preparation or the services of skilled craftsmen, and they are aesthetically pleasing, invoking feelings of stability, durability, and permanence. Besides being attractive and sturdy, they are generally small enough to be able to be lifted and manipulated by one person. They can range from about 6-120 pounds but more typically, though, they range around 35-70 pounds. In addition, they characteristically have only one facing or exposed face with an area in the range of about 0.17 to 1.00 square feet, and have corresponding volumes that range from about 126 to 2880 cubic inches. Such masonry blocks are commonly used to construct low retaining walls or planters, for example.
Most mortarless masonry blocks are manufactured using a process known in the trade as dry casting. With this process, block material having a comparatively low percentage of water (as opposed to block material that is wet cast) is deposited into an open-ended, unitary mold that is positioned on a palette and compacted by a movable piston as it moves towards the palette. Once the desired amount of compaction has been achieved, the compacted material is ejected or stripped from the mold by lifting the mold and/or moving the piston relative to the palette, or by vibrating the mold as it is moved away from the palette. The molded block is then cured outside of the mold in a series of separate steps.
This process allows many blocks to be manufactured in a comparatively rapid fashion because the molds are not required for the curing process. As will be understood, then, in order for these types of molds to be used most efficiently, they are usually constructed and arranged to facilitate extrusion or stripping. Most molds, therefore, comprise a vertically walled, unitary frame with no indentations or protrusions that would hinder extrusion or stripping. Blocks produced by such molds are usually symmetrically shaped so that the block may be subsequently split into two smaller, similarly shaped blocks, with each block having a substantially planar roughened facing. Alternatively, some molds may have walls with small transverse bottom ledges, or roughened divider walls, which are designed to work an uncured surface of a block as it is stripped from the mold. As will be understood, such ledges or divider walls are only capable of producing a substantially planar roughened surface, similar to the surfaces produced using the splitting technique described above.
A drawback with the afore-mentioned manufacturing techniques is that they are unable to produce a block that has a roughened facing that is bowed or curved with respect to the extrusion or stripping direction. If such a bowed facing is desired, the block must be worked after it has been stripped from the mold and cured, for example, by additional processing steps such as tumbling or grinding. As one may imagine, each additional processing step adds to the time and cost of the finished product.
A drawback with the afore-mentioned dry cast blocks is that that they are relatively small. This does not present much of a problem when retaining walls are less than 4 or 5 courses high. However, for retaining walls whose heights exceed 4 or 5 courses, it is usually necessary to provide stabilization devices to counteract the forces exerted by backfill material. Stabilization devices usually take the form of flexible sheets of a mesh-like synthetic material known in the trade as geo-grids, for example, which are usually positioned between courses of blocks and which extend horizontally and rearwardly into the backfill material that is being retained. Stabilization devices such as geo-grids may be connected to blocks by connectors, but usually they are frictionally retained in place between courses by the weight of the blocks pressing down on them. Often, it is necessary to provide stabilization devices for each course of blocks or for every other course of blocks, which adds to the cost of materials, labor, and time of construction. Unfortunately, stabilization devices can stretch, break, or be pulled out from the wall structure, which can lead to premature wall failure.
Another drawback common to most dry cast blocks is that they usually have only one facing or exposed face area. Thus, they are limited to a particular orientation within a structure. This limitation is underscored when the blocks are trapezoidal in shape, for example.
Another drawback common to most dry cast blocks is that they are designed and configured to engage vertically adjacent blocks in certain, predetermined arrangements. For example, some blocks are designed so that they can only be used to build vertical walls, while other blocks are designed so that they can only be used to build walls that have a predetermined batter or upwardly receding slope. Engagement between vertically adjacent blocks is most commonly achieved by providing blocks with integrally formed lips or protrusions that are designed to engage vertically adjacent blocks. Alternatively, engagement between vertically adjacent blocks may be achieved by providing connectors or pins that tie the blocks together.
Thus, there is a need for a masonry block that can be used to construct different wall structures. There is also a need for a masonry block that can be positioned in one of several predetermined orientations relative to vertically adjacent blocks to create different types of wall structures. There is also a need for a block that is able to engage vertically adjacent blocks without the use of extraneous devices or connectors. And, there is a need for a block that is capable of resisting normal forces without having to be operatively connected to stabilization devices such as geo-grids and/or earth anchors.